[ntp:questions] Trimble Resolution SMT on Ubuntu 12.04

Ron Frazier (NTP) timekeepingntplist at c3energy.com
Mon Mar 26 20:19:53 UTC 2012

Hi Geng,

I don't know if this will help or not, but the following things came to 
mind.  I am running Windows at the moment, but Linux should be similar.  
I plan to try all this in Ubuntu eventually.

When I was using NMEA only data, I had to have a bigger fudge factor, 
like this:

fudge time2 0.3710 refid GPS1                             

However, when I started using PPS, I found that the fudge factor was 
messing things up, so now I use this:

fudge time2 0.0000 refid GPS1                             
# use WITH PPS

Note that I stuck the fudge factor in there for readability.  However, 
its value is 0.

The other thing that occurred is that your clock may be too far out from 
gps time to begin with.  Try shutting down NTPD.  Note, if you compiled 
NTP yourself, the startup and shutdown scripts may not be in the right 
places.  I think the command is:

sudo /etc/init.d ntp stop

Then run this command to sync your clock with the NIST server in New 
York.  If you're not in the US, substitute another server name.

ntpdate -b nist1-ny.ustiming.org

Now your clock should be very close to NIST or UTC.

Now, restart NTPD.

sudo /etc/init.d ntp start

Wait a few minutes and run ntpq -p to see what's happening.

Also, make sure NTPD is reading the correct config file and that you 
don't have two of them around or something.

Finally, I'd recommend putting minpoll 4 maxpoll 4 on your NMEA line to 
match your PPS line.  I'm using a value of 3 on mine, which polls every 
8 seconds.



On 3/26/2012 12:06 PM, G wrote:
> I use Trimble Resolution SMT to sync time for a Ubuntu 12.04 server (kernel 3.2.0).
> Trimble send NMEA to /dev/ttyUSB1(9600 8N1) on Ubuntu  server
> PPS signal connect ACK pin on  /dev/parport0 . Ubuntu load Linux-PPS module( PPS_parport clear_wait=0) to create PPS device /dev/pps0
> I use verify the /dev/pps0  using rising edge by "ppstest /dev/pps0"
> --------------------------------------------------------------------------------------------
> trying PPS source "/dev/pps0"
> found PPS source "/dev/pps0"
> ok, found 1 source(s), now start fetching data...
> source 0 - assert 1332775909.500413150, sequence: 249302 - clear  0.000000000, sequence: 0
> source 0 - assert 1332775910.500456132, sequence: 249303 - clear  0.000000000, sequence: 0
> source 0 - assert 1332775911.500499213, sequence: 249304 - clear  0.000000000, sequence: 0
> -----------------------------------------------------------------------------------------------
> To verify the NMEA message , I link /dev/ttyUSB1 to /dev/gps1
> -----------------------------------------------------------------------------------------------
> #cat /dev/gps1
> $GPRMC,153343.000,A,4529.904930,N,07343.904831,W,0.241,325,260312,,,A*6F
> $GPGGA,153344.000,4529.905010,N,07343.904879,W,1,3,3.17,12.368,M,-32.087,M,,*5E
> ---------------------------------------------------------------------------------------------------
> I create the /etc/ntp.conf:
> -------------------------------------------------------------------------
> server mode 17 prefer       # NMEA RMC/GGA 9600bps
> fudge time2 0.01
> server minpoll 4 maxpoll 4  # PPS ATOM
> fudge flag2 0 flag3 1
> driftfile /var/lib/ntp/ntp.drift
> ------------------------------------------------------------------------------
> after ntpd run 48hours, ntpq -p:
>       remote           refid     st t when poll reach   delay   offset  jitter
> ==============================================================================
> xGPS_NMEA(1)     .GPS.            0 l   44   64  377    0.000  -214.54  25.464
> xPPS(0)          .PPS.            0 l   11   16  377    0.000  -174.60   4.981
> I have no idea why I got this result . what do I miss for config? by the way , I compile ntpd from source , not using ntpd from Ubuntu.
> Thanks for your time to read my question. give me some light please.
> regards,
> geng


(PS - If you email me and don't get a quick response, don't be concerned.
I get about 300 emails per day from alternate energy mailing lists and
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Ron Frazier
timekeepingdude AT c3energy.com

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